Along with the progress in cloud services provided by utilizing communication networks, the power consumption of datacenters serving as infrastructures for providing cloud systems has been increasing.
In a datacenter, many racks (server racks) are placed in a computer room, and a plurality of computers (servers) are housed in each rack. Moreover, jobs are organically distributed to the computers according to the states of operation of the computers to thereby process a large amount of jobs efficiently.
Computers generate a large amount of heat as the computers operate. Since high temperature inside a computer may be a cause of malfunction or failure, it is important to cool the computer. For this reason, a datacenter usually uses air blow fans to discharge heat generated by computers to the outside of their racks, and also uses a packaged air conditioner to adjust the temperature of the room.
Meanwhile, it has been said that the power consumption for air conditioning equipment accounts for approximately 40% of the whole electric power consumption of a datacenter. In order to reduce the power consumption of a datacenter without impairing the processing performance of the datacenter, it is important to efficiently cool the computers therein.
Packaged air conditioners may be capable of accurately controlling the temperature of air blown therefrom. However, with a packaged air conditioner, it is difficult to manage the temperature distribution in a room, so that locally excessively cooled areas and locally high temperature areas called hot spots may be formed. Moreover, since packaged air conditioners are distant from racks, the packaged air conditioners are preferred to have high air blowing performance, which has been a cause of increase in their power consumption.
In view of this, in addition to a packaged air conditioner, a system called In-Row is sometimes employed which involves disposing a cooling device between racks, the cooling device having substantially the same size as the racks. In this system, hot air discharged from the racks is cooled near the racks so as to reduce the occurrence of excessive cooling and the formation of hot spots and make the air conditioning equipment less power consuming.    Patent Document 1: Japanese Laid-open Patent Publication No. 2011-226737    Patent Document 2: Japanese Laid-open Patent Publication No. 2010-54074